2024-01-26 16:20:46
They are small, can be extremely annoying when they buzz around your ears, and feed on your blood: Mosquitoes, especially in summer, are simply a nuisance and have a remarkable ability to find their target. The reason for this is an extraordinarily sensitive sense of smell, which fundamentally changes previous knowledge and assumptions in science.
Mosquitoes have particularly sensitive noses
According to a new study at New York’s Rockefeller University, mosquitoes are particularly attracted to smells. And they perceive them very differently than previously thought. It was actually always assumed that each individual olfactory neuron in animals only carries one type of receptor. The latter reacts to chemical compounds in the air, is activated and causes the neuron to send a signal to the brain.
In the past, attempts were made to switch off these receptors and thus the signaling of smells in mosquitoes. But that was never successful and now we know why: their neurons carry several receptors. This means that the neurons can be activated by several different scents at the same time – so there are always alternatives.
Mosquitoes usually follow the CO2 emitted in our breath and body odors. And they consist of hundreds of fragrances, including alcohols and ammonia. Mosquitoes don’t care which ones tickle their neurons – the main thing is that there is one of them that gets them to their goal. However, there is also another, surprising cause of the penetrating insects.
Mosquitoes want to bite more often when Victim of Viruses are infected
Scientists at the University of Connecticut have taken a closer look at the connection between certain viral diseases and mosquitoes. They wanted to build on previous findings that insects are attracted to smells. It had also already been observed that mice suffering from malaria had an altered scent profile.
During the investigations, among other things, mosquitoes were released on mice with or without dengue and Zika viruses. The mosquitoes then moved to the infected rodents noticeably often. The same thing happened with people: the scent of a person suffering from dengue fever and a healthy person were placed on the hands of a test subject. The mosquitoes consistently preferred the hand with the “sick” scent.
Also good to know: In addition to the smell, there is also a visual component. We’ll therefore tell you which colors attract mosquitoes and which you shouldn’t wear in summer.
Acetophenone magically attracts mosquitoes
In tests with both mice and humans, it was found that the gaseous chemical compound acetophenone was present in particularly high concentrations in infected test subjects. And this substance attracted mosquitoes particularly strongly. However, this meant that it had to be sent out through the skin.
When comparing infected and healthy mice, an unusually high number of Bacillus bacteria was found in the sick animals, which in turn are among the main producers of acetophenone. From this, the researchers conclude that viruses change the scent of the host body by changing the microbiome of the skin.
Regulatory molecule is suppressed by viruses
Healthy skin usually produces high concentrations of the RELMα molecule, which has an antimicrobial effect. Only very low levels of RELMα were found in sick mice. The experts assume that this was caused by the virus infection and that this allowed Bacillus bacteria to spread unchecked. This led to high acetophenone production, which attracted mosquitoes.
The mosquitoes then absorb the virus in the blood and pass it on. In this way, the pathogen takes an active part in its spread. The investigations mainly focused on dengue and Zika virus infections. It is therefore unclear whether other viruses can also cause similar effects.
What could help against this?
In their studies, the researchers also considered whether and how the virus-related mechanism that attracts mosquitoes so much can be prevented. To do this, the active ingredient isotretinoin was turned to. This is part of vitamin A metabolism and contributes to the production of RELMα.
In experiments with mice, treatment with isotretinoin clearly had an effect. The RELMα concentration increased, that of Bacillus bacteria decreased. Mosquitoes did not react any more aggressively than to other, uninfected mice.
Next on the agenda are tests with human candidates. If these are positive, simple therapies could be developed in the future. Overall, these could help reduce mosquito-borne virus infections.
Quelle: „A volatile from the skin microbiota of flavivirus-infected hosts promotes mosquito attractiveness“ (Cell, 2022)
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